Thursday, 18 August 2011

Live traps reveal small mammals

The rich, waist high vegetation of the riverside meadow has proved a good hunting ground. The small mammal traps deployed here over the weekend have yielded good numbers of mice, voles and shrews. Other traps, set along a woodland edge, have proved equally successfully. The traps were being used as part of a workshop on small mammal identification and trapping, organised by the Norfolk & Norwich Naturalists’ Society to give more people the skills and confidence to get involved in wildlife recording. Small mammals are a group that I have worked on for many years, so it was rewarding to be able to pass on some of my skills to a new generation of small mammal enthusiasts.

The traps, known as Longworths, consist of a small aluminium nest box, attached to a tube that contains a trap door and a trigger. A small mammal entering the box, trips the door and then is caught and held until the traps are checked a few hours later. In the meantime, the mouse, vole or shrew has bedding and food available, which seems fair compensation for its inconvenience.

The woodland edge traps were dominated by captures of Bank Vole, neat creatures with rich, chestnut red fur in the adults. Also present in a smaller proportion of the traps were Wood Mouse and Common Shrew. The success of these traps was remarkable; with two traps set at each of the trap points we managed to catch in every trap and, incredibly, we even managed to catch two animals (a Wood Mouse and a Bank Vole) together in one trap. This high capture rate ensured that each of the dozen participants got to see and handle various small mammals. Handling your first small mammal, especially when the eyes of the rest of the group are on you, is not the easiest thing in the world but folk grew in confidence as the morning progressed. The riverside traps were dominated by captures of Field Vole, hardly surprising since the rank vegetation was classic Field Vole habitat and the matted vegetation dominated by their network of interconnected runs.

Each trap was emptied in turn into a large, clear polythene bag. This allows you to see what you have caught and then to manoeuvre it into the corner of the bag where it can be more easily removed. This involves holding the small mammal very gently through the bag with one hand, while the other is placed in the bag, your finger and thumb used to pick the animal up by the baggy skin at the back of the neck. This provides a brief opportunity to determine age, sex and breeding condition before release. It was a morning well spent.

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